KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/include/asm-generic/irq_regs.h b/include/asm-generic/irq_regs.h
new file mode 100644
index 000000000..2e7c6e89d
--- /dev/null
+++ b/include/asm-generic/irq_regs.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Fallback per-CPU frame pointer holder
+ *
+ * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifndef _ASM_GENERIC_IRQ_REGS_H
+#define _ASM_GENERIC_IRQ_REGS_H
+
+#include <linux/percpu.h>
+
+/*
+ * Per-cpu current frame pointer - the location of the last exception frame on
+ * the stack
+ */
+DECLARE_PER_CPU(struct pt_regs *, __irq_regs);
+
+static inline struct pt_regs *get_irq_regs(void)
+{
+	return __this_cpu_read(__irq_regs);
+}
+
+static inline struct pt_regs *set_irq_regs(struct pt_regs *new_regs)
+{
+	struct pt_regs *old_regs;
+
+	old_regs = __this_cpu_read(__irq_regs);
+	__this_cpu_write(__irq_regs, new_regs);
+	return old_regs;
+}
+
+#endif /* _ASM_GENERIC_IRQ_REGS_H */